1. Field of the Invention
This invention relates generally to the field of battery-powered audio electronic devices. More particularly, the invention relates to the generation of warning signals to the users of battery operated electronic devices such as hearing aids of the impending need to replace batteries, and specifically to the field of providing a low battery power condition detector capable of generating an audible warning and initiating subsequent system shutdown in such devices if necessary.
2. The Background Art
Battery operated electronic devices are commonly known in the art. As is known to those skilled in the art, battery operated electronic devices for audio applications may suffer a sound quality loss as the batteries begin to reach a stage of depletion. For example, in the case of battery operated hearing aid devices, once the charge on the hearing aid battery is depleted beyond a certain point, the hearing aid no longer functions normally. At this point, the user of the device may experience a reduced benefit, or in some cases even an adverse effect, from the device. In some instances, the user may experience such reduced benefits or adverse effects as a drop in the amplification gain of the device, a reduced output volume, an extreme distortion or noise, increased noise, or even the generation of uncomfortable and intolerable sounds. Such a sudden loss of normal operation in a hearing aid device owing to battery depletion without any forewarning could pose a dangerous hazard, not only to the user but also to individuals in close proximity to the user. Harm caused to the other individuals occurs in several instances, especially where a user is operating a motor vehicle or heavy machinery.
In the field of battery operated audio electronic devices such as hearing devices, there is a current lack of systems with built-in annunciation mechanisms which can assist in the generation of a warning signal to the user to indicate that the battery in the hearing aid device is running low and needs replacement. Most systems known in the art for implementing low battery warning systems in hearing aids may provide a single fixed voltage comparison threshold to which the battery output voltage is compared. However, the difficulty encountered in these systems is that a single fixed voltage may not necessarily provide the optimum tradeoff between long battery life and adequate warning time for the user. An additional problem posing some of these systems is that increase of a battery's internal impedance as it approaches the end of its life makes the hearing aid susceptible to large voltage transients at its power supply. These transients could falsely trigger the low battery detector typically used in such systems, and reduce the perceived battery life of the hearing aid.
Thus, a need exists for an electronic hearing aid device which could, with the help of such an annunciation mechanism, detect a low battery condition and provide an audible warning to the user while the battery is charged sufficiently such that the hearing aid device is still able to continue its normal operation. Moreover, such a mechanism should be able to confirm that a low battery condition actually exists before generating such a warning, so that a user is not falsely warned that the batteries need replacing. Finally, because circuit area is limited in electronic devices such as those used in hearing aid applications, the circuitry used to implement such an annunciation mechanism should be capable of being shared for other purposes. Unfortunately, no current mechanism exists to provide these functions and enable these activities.
The present invention provides a built-in low battery power detection system for use in electronic devices such as hearing aids that generates audible warnings to the user to indicate a low battery power condition. According to aspects of the present invention, the user is afforded an opportunity to replace the batteries of the hearing aid device before an adverse loss of operation occurs. According to other aspects of the present invention, the electronic device is further designed to shut down in a predictable and comfortable manner at some time after the generation of the low battery warning, thus protecting the user against the generation of uncomfortable sonic artifacts. The current invention can be used in any battery powered audio electronic device, including hearing devices and other similar communication equipment.
Thus, the present invention provides a built-in system to detect a low battery power condition and to generate audible warning signals to indicate that the battery is low. However, even after generation of such warnings signal, the electronic device continues to function normally for some time. If this preliminary warning indicating low battery goes unheeded by the user and he/she fails to replace the battery, the system may generate a final warning and subsequently shut down the audio output stage of the electronic device. However, until this final warning is generated, the hearing aid device essentially continues to function normally, without at any instant compromising of the effective functioning of the device. Thus, even when total battery depletion causes the shut down of the electronic device, there are no adverse effects to the user. These and other features and advantages of the present invention will be presented in more detail in the following specification of the invention and in the associated figures.